1. Field of the Disclosure
The disclosure relates to an optical branching element and an optical branching circuit that use optical waveguides.
2. Description of the Related Art
Techniques have been disclosed, which reduce loss in conventional optical branching elements using optical waveguides by providing strip-like waveguides to branched waveguides. For example, in Japanese Patent No. 3338356, Japanese Patent No. 4385224, and Japanese Patent Application Laid-open No. 2004-325865, strip-like waveguides are provided in a portion from a slab waveguide to an arrayed waveguide of an arrayed waveguide grating (AWG) to reduce the loss. In Japanese Patent Application Laid-open No. 2006-023623, strip-like waveguides are provided in a portion from a tapered waveguide to a branched waveguide of a Y-branched optical branching element to reduce the loss.
However, when the inventors of the present application fabricated Y-branched optical branching elements having strip-like waveguides and carefully examined their characteristics, there was a problem that a desired loss reduction predicted from their designs was not achieved in some cases.
Accordingly, there is a need to provide an optical branching element and an optical branching circuit that are able to achieve reduction of the loss even further.